Dust Properties in the Galactic Bulge

TL;DR

This study investigates whether the dust extinction ratio in the Galactic bulge differs from the local neighborhood and finds it to be consistent with the standard value RV=3.1, challenging previous suggestions of variation.

Contribution

The paper provides observational evidence that the total-to-selective extinction ratio in the Galactic bulge is similar to the local value, using mid-infrared hydrogen lines and nebular analysis.

Findings

RV in the Galactic bulge is consistent with 3.1

No significant difference in dust properties between bulge and local neighborhood

Supports the use of standard extinction laws in the Galactic bulge

Abstract

It has been suggested that the ratio of total-to-selective extinction RV in dust in the interstellar medium differs in the Galactic bulge from its value in the local neighborhood. We attempt to test this suggestion. The mid-infrared hydrogen lines in 16 Galactic bulge PNe measured by the Spitzer Space Telescope are used to determine the extinction corrected H{\beta} flux. This is compared to the observed H{\beta} flux to obtain the total extinction at H{\beta}. The selective extinction is obtained from the observed Balmer decrement in these nebulae. The value of RV can then be found. The ratio of total-to-selective extinction in the Galactic bulge is consistent with the value RV =3.1, which is the same as has been found in the local neighborhood. We conclude that the suggestion that RV is different in the Galactic bulge is incorrect. The reasons for this are discussed.